A known method for detecting a seating state of an occupant at a seat for a vehicle includes monitoring a deviation of a load generated at the seat, that is, a deviation of a seat load. For example, at a side airbag control apparatus described in JP2008-143481A1 (which will be hereinafter referred to as Patent reference 1), a load sensor is provided at each of four leg portions supporting a seat of a vehicle. In Patent reference 1, an entire seat load is detected by adding together sensor load detection values of the four sensors. Further, with the use of the two load sensors positioned at a vehicle-width direction outer side, the load detection value at the vehicle-width direction outer side is obtained. A width-direction load ratio of the seat is calculated by dividing the load detection value at the vehicle-width direction outer side by the entire seat load.
In this case, the larger the width-direction load ratio is, it is determined that the more the seat load is deviated towards the vehicle-width direction outer side. Further, in Patent reference 1, in a case where the width-direction load ratio exceeds a predetermined threshold value, it is determined that an occupant at the seat is seated while being deviated significantly towards the vehicle width-direction outer side. In such a case, a side airbag is prohibited from being inflated, thereby allowing the side airbag to function more effectively.
However, in such an airbag inflation control described above, contents of the control have always been improved. In addition, recently, a seating posture and/or a seating position of the occupant at the seat are considered not only in the airbag inflation control but also in various fields of control. Thus, because a more detailed seating state of the occupant is required to be obtained with regard to occupant detection, there remains room for improvement in this aspect.
A need thus exists for an occupant detection method and an occupant detection apparatus, which are not susceptible to the drawback mentioned above.